Here is a couple of pictures of sewage backing up out of the drainfield. It is full of bacteria and pathogens. That is what is making that black tar color. This has been going on for some time. It kinda dries up in the summer but it’s still smelly and gross. And is contaminating surface to ground water. This drainfield needs dug up and find out what’s going on. Chances are this drainfield has reached the end of it’s life.